What is a herring?
A search right here might have helped. I did the research when the Massachusetts river herring moratorium went into effect.
There were so many returns on the keyword herring I had to plug in copepods
The sea run herrings primary diet .
The single most important copepod is [Zooplankton (Calanus finmarchicus)] its the basic food for the local mackeral, river herring, alewife and shad.
The herring are dependent on these food sources to such a degree that herring scientists have proposed that information on prey species may provide a method to predict the location of herring stocks.
There are 9 different species in the Gulf of Maine.